The fact is that the majority of hand ndash;held audio playback devices simply aren rsquo;t capable of adequately powering many of today rsquo;s quality headphones. This is because headphones present a definite challenge to amplifier designers. There are two basic types: the Over ndash;Ear #40;OE #41; in general use in the recording industry and the smaller In ndash;Ear #40;IE #41; a.k.a. `ear ndash;bud` type commonly used with portable devices such as MP3 players. Given the range of available OE and IE headphones in attempting to accommodate them all your mobile device rsquo;s headphone output is optimized for none. Typically OE types exhibit sensitivities of about 100dB #47;mW whereas IE devices can be 10dB higher or more e.g. 110dB #47;mW . Assuming a 10dB difference the lower sensitivity OE headphones require ten times more power to achieve the same volume as the IE type. If you rsquo;re using OE headphones you rsquo;ll really appreciate the NuForce MMP power capability. Your headphones will sound distinctly clearer and more natural. Just connect the MMP to the headphone output of your MP3 player Smartphone iDevice etc. and finally start experiencing the higher level of performance your headphones were always capable of.